This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Function of Tubules-1”.
1. PCT is lined by which of the following cells?
a) Brush border columnar cells
b) Brush border cuboidal cells
c) Ciliated cuboidal cells
d) Ciliated columnar cells
Explanation: PCT is lined by simple cuboidal brush border epithelium which increases the surface area for reabsorption. Nearly all of the essential nutrients are reabsorbed here.
2. Which of the following is not reabsorbed in the PCT segment?
Explanation: Nearly all the essential nutrients, 70-80% of electrolytes and water are reabsorbed by this segment. Absorption of HCO3– also takes place here.
3. Which of the following is not correct regarding PCT?
a) It does not maintain the pH
b) It maintains the ionic balance of the body
c) It absorbs HCO3– ions
d) It secretes potassium ions
Explanation: PCT is responsible for maintaining the pH of the body fluids. It is also responsible for maintaining the ionic balance of the body fluids by selective secretion of hydrogen ions, ammonia, and potassium ions into the filtrate. It also absorbs HCO3– ions to maintain the ionic balance.
4. In which renal tubule, the reabsorption is minimum?
a) Descending limb of Henle’s loop
c) Collecting tubule
d) Ascending limb of Henle’s loop
Explanation: Reabsorption of water is minimum in ascending limb of Henle’s loop as it is impermeable to water which means that it does not allow the movement of water through itself.
5. The descending loop of Henle is impermeable to water.
Explanation: The descending limb of the loop of Henle is permeable to water. It means that water can easily pass the loop. But the descending limb is almost impermeable to electrolytes which means it does not allow the movement of electrolytes through itself.
6. How does the ascending loop of Henle allow the movement of electrolytes?
a) Only active transport
b) Only passive transport
c) By both active and passive transport
d) Only by diffusion
Explanation: The ascending limb of Henle’s loop is impermeable to water but allows the transport of electrolytes actively or passively. Moreover, the width of this tubule also varies as it has a thin segment and a thick segment of the ascending limb.
7. What happens when the filtrate passes through the ascending loop of Henle?
a) It gets dilute
b) It gets concentrated
c) No effect
d) It reverts back
Explanation: As the ascending limb is impermeable to water, therefore as the concentrated filtrate from the descending limb passes upwards, then it gets diluted due to the passage of electrolytes to the medullary fluid.
8. Which of the following is reabsorbed completely in the PCT?
a) Amino acids
c) Ascorbic acid
d) Sodium ions
Explanation: Glucose is reabsorbed completely in the PCT by active transport. 70-80% of water is reabsorbed by osmosis while 70% sodium, potassium, and calcium ions are actively transported.
9. Is the nephric filtrate present in which segment of the renal tubule is isotonic to plasma?
a) Collecting duct
b) Collecting tubule
Explanation: The nephric filtrate present in the PCT is isotonic to blood plasma i.e. 300 mOsmol/L. In PCT, there is obligatory reabsorption of water, i.e., absorption without the influence of any hormone.
10. Which of the following does not show maximum osmolarity?
a) Tip of Henle’s loop
b) Interstitial fluid
d) Collecting duct
Explanation: The tip of Henle’s loop, interstitial fluid, and collecting duct show maximum osmolarity i.e. 1200 mOsmol/L. All of these structures are present in the inner medullary regions of the kidney.
11. If the loop of Henle is removed, hypertonic urine will be produced.
Explanation: If the loop of Henle is removed, hypotonic urine will be produced as water will not be reabsorbed as in descending Henle’s loop, 5-10% of the water reabsorption takes place.
12. On which segment onwards, the nephric filtrate is called as urine?
c) Collecting duct
Explanation: DCT onwards, the nephric filtrate is called urine. In the last part or segment of the collecting duct, almost 99 per cent of the reabsorption of nephric filtrate has taken place.
13. The passage of which of the following makes the urine hypertonic?
a) Sodium ions
d) Potassium ions
Explanation: In the last segment of the collecting duct, urea goes into the interstitial fluid, and there enters to ascending Henle’s loop which further comes to the interstitial fluid by collecting tubule and duct making the whole collecting duct permeable for water and thus making the urine hypertonic.
14. What is the normal amount of urea in the blood?
a) 10-15 mg/100 ml
b) 18-38 mg/100 ml
c) 40-50 mg/100 ml
d) 0.2-0.5 mg/100 ml
Explanation: The normal amount of urea present in the blood is 18-38 mg/100 ml of the blood. The increase in the amount of urea in the blood is termed as uremia.
15. What is the percentage of urea present in the urine?
Explanation: The composition of urine is as follows- 96% of water, 2% of urea, and the rest 2% comprise of uric acid, ammonia, hydrogen ions, potassium ions, hippuric acid, creatinine, creatinine sulphate, drugs, and antibiotics.
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